Acoustic cover part for a vehicle

Abstract

A cover part for a vehicle, especially an underbody cover, has a porous core layer and at least one cover layer on each side, wherein the porous core layer is constructed such that it has acoustic transparency or an acoustically absorbent effect. Here, the porous core layer is made either from a thermoplastic matrix with embedded reinforcement fibers, especially glass fibers, whose melting point temperature is higher than the melting point temperature of the plastic matrix, or from a foam, which is either open-cell or closed-cell and perforated. The acoustically absorbent porous core layer is occupied on one or both sides with one or more acoustically transparent or absorbent covering layers.

Description

[0001]This application is a national stage application that claims priority under 35 U.S.C. §§365 and 371 to PCT / EP05 / 11820, filed Nov. 4, 2005, which claims priority to DE 10 2004 053 751.8, filed Nov. 6, 2004.FIELD OF THE INVENTION[0002]The invention relates to a cover part for a vehicle and especially to an engine compartment part or underbody cover part for a motor vehicle, which shall be used as the basis for examples below.BACKGROUND OF THE INVENTION[0003]It is known to form underbody covers or engine compartment covers from glass fiber-reinforced plastics in a forming method with high internal mold pressures. The glass-fiber reinforcement typically consists of woven mats or nonwoven mats, but also from bulk glass fibers, which are, however, as non-oriented as possible and which are introduced into a plastic matrix predominantly of polypropylene. The semifinished products made available in this way are usually plates made from glass fiber-reinforced thermoplastic (GMT) or rod-...

AI Technical Summary

Benefits of technology

[0014]According to the invention, the components of glass fiber-reinforced support plates, sound absorbers, heat insulators, nonwoven linings, etc., are no longer separated in their functional arrangement and in their successive production. The properties are combined in a single material or layer arrangement, wherein in a single shaping process an engine compartment cover, an underbody cover, a wheel well, or other inherently stiff components are produced from such a material composite. This results in clear cost reductions compared with most well known multiple-step production methods. Finally, with respect to current developments for always using increasingly larger surface-area components in the underbody region, an advantageous method requires no compromises in this respect and allows, for example, the production of a completely closed underbody assembly made from a single large plate.

[0015]The method according to the invention offers the prerequisites for creating components having all of the properties named above, wherein both the production is simplified and thus less expensive and also the functional properties can be maintained or even increased.

[0016]The basic idea of the invention is to combine a porous core layer with acoustically transparent or absorbent cover layers such that both the mechanical properties of classic support materials and also the acoustic properties of classic absorbers are realized. Thus, the support itself becomes an absorber and contributes with its material strength to the effective acoustic total thickness of the component. However, the effective acoustic surface is also increased, because now the areas that were not previously equipped with additional absorbers due to installation space are now also acoustically active. Additional absorbers to be attached at a later time are no longer necessary.

[0021]Open-celled, porous materials, such as foams and nonwovens, are acoustically absorbent if their flow resistance assumes certain parameters. For nonwovens, the setting of this flow resistance is typically realized by suitable compaction of the fibers. The PP glass fiber mixture of an LWRT core can also be compressed suitably and thus allows this acoustic adjustability, wherein the reinforcing properties of the bound glass-fiber structure are maintained.

Problems solved by technology

The maximum component size currently possible is approximately 1.0 to 1.5 m2, due to the very high molding pressures of approximately 200-300 bar and the associated high machine costs for presses with a pressing force of more than 3000 t.

A disadvantage in this method is that structures for reinforcing or required for additional functionality, such as connecting pieces, NACA openings, attachment domes, etc., can be attached only to a limited extent, if at all.

However, it is also known to produce a complete noise enclosure, that is, a support and compartment absorber, in a blow-molding method in one processing step.

However, based on the process, this creates a considerable restriction on the material selection of the support and absorber and thus also on the physical properties, especially as concerns glass-fiber reinforcement of this component and its properties with reference to stiffness, strength, and impact resistance.

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